Arsenal won the league with 78 points in the 1997-98 season, becoming the only other club to match United, and Pellegrini said this season's title could won by a team with one of the lowest points totals on record.
"It is a very difficult title to win because the amount of points all the teams have now is not normal," the Chilean told reporters after his side's 2-1 win over Swansea City at the weekend.
"You don't have that in every Premier League season. Maybe this season the teams are stronger, maybe the games are closer.
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"Every season is different but to win the Premier League this season will be very difficult and take less than 80 points.
Pellegrini also suggested that he was more concerned with ensuring domestic success than winning the Champions League.
"I always think the Premier League is the most important," he said. "In the Champions League you can have a bad game, go out in the semi-final and nobody remembers what you did.
"The Premier League is the work of the whole year. I always say it must not be an obsession to win the Champions League.
"It's a very important title and beautiful to do it but you must not try to win that and lose focus on the Premier League."
(Reporting by Simon Jennings in Bengaluru; editing by Sudipto Ganguly)
